Microwave radiofrequency transmission devices are designed to operate at many different frequencies. The frequency for any microwave radiofrequency transmission device is largely a function of a crystal oscillator that provides a timing signal to the circuit. In many microwave circuits and within a relatively broad range of operation, it is possible to use the same basic circuitry to emit microwave signals having many different principal frequencies. Thus, by using different oscillators with the same basic circuitry it is possible to interchange crystal oscillators to have the circuit emit different microwave signals. Circuits with this flexibility use removable crystal oscillators that plug into sockets that are pre-positioned in the printed circuit board. This design is an economical and practical way to increase microwave module assembly flexibility.
A limitation, however, exists with this design. In most crystal oscillator designs, only three leads plug into three sockets of the circuit board. These three leads make a good connection with board circuitry when the crystal oscillator is fully positioned within the sockets, but may come loose and thereby disconnect the crystal oscillator. Once the crystal oscillator falls out of the circuit board, the microwave device becomes fully non-operational. It is an object of the present invention, therefore, to provide a way to retain the crystal oscillator in pre-positioned sockets of a circuit board.
There are known ways to retain removable crystal oscillators and other similar devices securely plugged into a circuit board. The conventional apparatus is a metal retaining arm device that includes a rubber pad or grommet to contact and direct the crystal oscillator into its socket. The metal retaining arm is screwed into the circuit board using a small screw.
Limitations with this design are numerous, but at least include the following problems. First of all, the metal retaining arm device comprises at least three parts. The first part is the metal retaining arm itself, the second is the rubber grommet, and the third is the fastening and positioning screw. For this device, the fastening and positioning screw must have a screwhole that is fabricated into the printed circuit board. The costs associated with this device include assembling the rubber grommet into the metal retaining arm, installing the screw in the circuit board, forming the screwhole within the circuit board, and positioning the metal retaining arm and rubber grommet over the crystal oscillator. Another limitation of the prior art metal retaining arm device is that the base of the retaining arm and the screwhole require circuit board space or "real estate" that could be used more effectively for other components or, similarly, could be avoided to make the circuit board smaller.
It is a further object of the present invention, therefore, to provide a retainer for a removable crystal oscillator or other component that significantly reduces the complexity of conventional devices.
It is yet another object of the present invention to avoid waste of circuit board real estate by removing from the circuit board the screwhole and avoiding the need for the space that accommodates the metal retaining arm.
It is, thus, an object of the present invention to provide a retainer that retains the leads of removable circuit board components such as a crystal oscillator in a plurality of associated sockets on the circuit board. This is done by the retainer having a retaining surface that applies a retaining force to the component. The retaining force includes a spring force that directs the plurality of leads into the associated sockets. A positioning surface on the retaining clip positions the retaining surface in association with the component by engaging the positioning surface with an exposed exterior surface of the associated sockets. A connecting surface connects the retaining surface with the positioning surface around the circuit board and assists in maintaining the retaining force against the component.
The retaining clip is made of an insulating material that has an elastic memory for constantly applying the retaining force against the component. Although the preferred embodiment of the retainer is a clip for retaining crystal oscillators on a circuit board, the retainer has many potential uses for any other components that plug into sockets on a circuit board.